Positive let-off motions for looms



Dec. 31', 1963 T. HlNDLE ETAL 351155901 POSITIVE LET-OFF MOTIONS FOR LOOMS Filed Feb. 25, 1961 1 e shets-sne't 1 QMQ Q Dec. 31, 1963 T. HINDLE ETAL 3,115,901

' POSITIVE LET-OFF MOTIONS FOR LOOMS Filed Feb. 23, 1961 v 6 Sheets-Sheet 2 Filed Feb. 23, 1961 Dec. 31; 1963 T. HINDLE ETAL 3,115,901

POSITIVE LET-OFF MOTIONS FOR LOOMS 6 Sheets-Sheet 3 Hllllli ll FIG.3.

INVENTORS Dec. 31, 1963 T. HINDLE ETAL 3,115,901

POSITIVE LET-OFF MOTIONS FOR LOOMS Filed Feb. 23, 1961 e Sheets-Sheet 4 INVENTORS iii/0m; filial/e Java! fi. flarzia w w @m Dec. 31, 1963 T. HINDLE ETAL 0 POSITIVE LET-OFF MOTIONS FOR LOOMS Filed Feb. 25, 1961 Q 6 Sheets-Sheet. 5

FIG. 2

Dec. 31, 1963 T. HINDLE ETAL POSITIVE LET-OFF MOTIONS FOR LOOMS s Sheets-She et 6 Filed Feb 2:5, 196i a B F United States Patent 3,115,991 POSITIVE LET-OFF MGTIONS F'QR'LOOMS Thomas Hindle, Thornlea, Beardwood Brow, Blackburn, England, and David D. Banks, Hillberry,

Preston Old Road, Feniscowles, near Blackburn,

England Filed Feb. 23, 1961, Ser. No. 91,127 Claims priority, appiication Great Britain Feb. 25, 1960 3 Claims. (Cl. 139-110) This invention relates to positive let-off motions for looms, that is to say, let-off motions in which the warpbeam is positively driven to unwind the warp whereby the warp is maintained at substantially uniform tension in response to a warp tension device such as a sensitive back-rest.

The primary purpose of a let-off motion is to unwind the warp at an average rate 'which is in step with the average rate at which the warp is being woven into cloth and drawn away by the cloth take-up motion at the front .of the loom. This is effected by maintaining a normal length of warp between the beam and the take-up motion of the loom, such normal length including a tolerance to reduce the frequency of operation of such let-off motion.

Such let-off motions may be broadly divided into two groups. In the first of these, the let-off acts to rotate the beam a suitable amount-either more or lessduring every consecutive pick or crankshaft revolution. In the second group, the warp is positively unwound intermittently, the let-off action then ceasing for a variable number of picks according to a predetermined working tolerance until it is again caused to operate to let-ofi more warp. Such action is obtainable by control mechanism responsive to positional change of a sensitive back-rest over which the warp passes from the beam intothe loom.

The present invention relates specifically to a let-off motion belonging to the second group, and is particularly convenient for use in connection with very wide and heavy looms as required for weavingpaper-machine felts. .Suc h looms may attain a weaving width of .80 "feet or even more, and it is of paramount importance that the felts woven thereon shall be, within very narrow limits, .perfectly uniform as regards both tension and density of warp and weft.

In weaving such felts, it is necessary, at the end of each felt length, to leave a fringe of warp yarnof a specified length, free from interwoven weft, by which means each felt is subsequently made endless by hand-splicing. The aforesaid fringing operation is preferably carried out with the loom crankshaft stationary, 'by actuating the cloth take-up motion forwardly either 'by hand or preferably by a separate electric motor through suitable reduction gearing. During each such fringing operation, the warp should desirably be unwound from the beam-at a rate commensurate with the rate of take-up and consistent with maintenance of the pre-determined warp tension, so as to permit resumption of weaving after the desired length of warp fringe has been provided. In known practice, however, the warp beam let-off and warp tension means has to be manually adjusted after each such fringing operation.

Furthermore, in the event of a weaving fault being detected in the woven felt adjacent to the cloth fell, it is occasionally necessary to unweave until the fault has beeneradicated, and then restore normal conditions preparatory to resuming weaving. If only a small number of weft picks need to be abstracted in order to remove the faulty pick of weft, then the loom is preferably turnedover in reverse, a pick at a time, so enabling the intervening weft and finally the faulty weft to be removed. During such reversal or back wind of the loom and its geared components, the take-up, dobby and box-motion all reverse their rotation and thereby maintain their essential positional synchronism with the loom crankshaft, in readiness forimmediate resumption of weaving. A difficulty still exists, however, inasmuch that the warp beam, in known.practice,requires to be manually adjusted (back wound) progressively with the reverse rotation of the loom to maintain or restore correct weaving tension in the warp.

Moreover, if removal of the weft fault would necessitate too long an unweaving turning back operation in the above manner, it is usual to cut back the woven Weft at suitable intervals across the woven cloth to enable the weft fragments to be readily pulled'out by hand, thereby leaving the warp available for weaving-in new weft. Here .again, apart from synchronising the dobby and box-motion, the difliculty exists that after such removal of the wveft fragments the warp beam as well as the take-up have to be manually reversed or wound back and adjusted to provide correct weaving tension with the cloth fell in 'firm contact with the reed in its fully forward position. Unless these manual operations of reversing the take-up motion and winding-back the beam are mutually accommodating, their manual operation easily results in failure to restore and maintain uniformity of warp tension and this causes weaving defects in the Woven fabric.

It the case where the warp tension and positive let-off motion are controlled by a sensitive back-rest, a further .problem exists in that the shock of beat-up of the reed against the fell of the cloth causes bouncing of the back-rest, and this redundant movement prejudices the action of the automatic let-off mechanism controlled normally by the position of the back-rest, so that the setting of such control is limited or desensitised by the necessity to'avoid too frequentactuation of such let-off mechanism.

The principal object of the-present invention-is to pro- .vide an improved positive warp let-off motion controlled by a sensitive back-rest and characterised by the let-off, .in its preferred form, being actuated by its own reversible electric motor which is equipped with an electro-magnetic brake and contactor switchgear so as to be capable of operation, as and when required under automatic control, irrespective of whether the loom crankshaft is revolving or stationary at the time, the said electric motor being controlled so as to let-off warp from the beam in response .to a detected and signalled lengthdeficiency, or to backwind it onto the beam in response to a signalled length excess of warp, or alternatively, to remain inactive so long as the warp length from the beam to the take-up motion is within predetermined normal limits of length, all as detected by and signalled, for example, by a sensitive back-rest.

A secondary object of the present invention is to obviate the necessity, hitherto existing, for manual adjustment of the warp beam, or take-up motion and warp beam, in order to restore correct weaving conditions prior to resumption of normal weaving after effecting the aforesaid fringing operations, also after unweaving, for the ,purpose of eradicating a weft fault from the woven cloth in the aforementioned manner.

Another object of the invention is to obviate the disadvantages arising from the above-described bouncing of the sensitive back-rest.

The invention is based upon an appreciation of the afore-mentioned factors which give rise to the problems aforesaid.

According to one feature of the invention, the positive let-off motion for the loom comprises powered beamturning mechanism adapted to turn the beam; a movable length-sensitive means engaged with the warp and which is responsive to change of warp length from a normal length between the warp beam and the take-up motion of the loom, and control means operably connecting said length-sensitive means and said beam-turning mechanism so as to activate the latter for rotation of the beam on change of said normal length and to stop rotation on restoration of such normal length characterised in that the beam-turning mechanism is powered other than from the crankshaft and is constructed for rotating the beam for back-wind as well as for let-off and in that the control means is selectively responsive to increase as well as to decrease of said normal length so as to initiate and stop rotation of the beam in the required direction and for the required rotation to restore the said normal length.

The expression normal length is used herein to define a length of warp (between reasonable minimum and maximum limits of length), which can be maintained without hunting of the let-off mechanism, or unduly frequent actuation thereat, or without unduly infrequent actuation thereof prejudicial to the maintenance of substantially uniform warp tension.

The beam-turning means referred to may be actuated by fluid pressure or electric power, but in any case, is powered separately from the normal drive to the loom crankshaft, so that it is operative whether or not the crankshaft is rotated.

In a preferred embodiment of the invention, the beamturning means comprises a reversible electric motor equipped with an electromagnetic brake and control means therefor operable by a movable warp-tensioning and length-sensitive back-rest comprising relay-held alternative forward and reverse switches therefor, and a relay release or stop switch intermediate said forward and reverse switches.

The improved positive let-oif motion preferably includes tension-compensating means to maintain uniformity of tension in the warp across the loom, in spite of change of angularity of the warp between the beam and the movable back-rest with the relative changes of position of the latter necessary for control of the let-off mechanism. For this latter purpose it is preferred to use the construction of sensitive back-rest which is the subject of copending United States application for Letters Patent, Serial No. 90,800, filed February 21, 1961, by Thomas Hindle and which is briefly described hereinafter.

According to a second feature of the invention, means is provided for obviating the displacement of the sensitive back-rest by reason of the shock-load when the reed beats up the weft into the cloth.

In a preferred embodiment of this feature of the invention, hydraulic locking mechanism is provided, synr chronised with the loom crankshaft, to lock the back-rest momentarily in the position it occupies at the time, and thereby to prevent violent displacement of the back-rest by the beat-up shock load.

In the accompanying drawings:

FIG. 1 is an end elevation showing one example of a positive let-off motion in accordance with the present invention;

FIG. 2 is a plan of the construction shown in FIG. 1 with parts of the mechanism removed for clarity, but the position of some indicated by broken lines;

FIG. 3 is a rear elevation;

FIG. 4 is a fragmentary rear elevation showing the electric control switch actuating mechanism;

FIG. 5 is a front view of the control switches;

FIG. 6 is an electric circuit diagram;

FIG. 7 is a rear elevation showing a mod iication of the construction shown in the previous figures;

FIG. 8 is a timing diagram; and

FIG. 9 is a wiring diagram applicable to the modification of FIG. 7.

As shown in the drawings, the warp beam 10 carries a warp, the location of runs of warp yarns extending from the warp beam to a fixed guide bar 120 (corresponding to maximum and minimum diameters respectively, of the 4 warp mass on the beam) being indicated, respectively, at 11a and 11b. The beam-turning mechanism comprises a reversible electric motor 13, fitted with an electro-magnetic brake, driving through reduction gear box 13a, shaft 14 with worm 15 and a complementary worm-wheel 16 on the beam.

The electro-magnetic friction brake referred to (not shown) is of known type which is applied by the springs and released by an electro-magnet. The magnet coils are connected in parallel with the electric motor terminals so that both are switched on and off together.

The whip roll or back-rest, as here illustrated, comprises an elongated, rigid, hollow cylinder or tube 12. having its axis parallel to that of the warp beam and carried by a lever assembly comprising a plurality of like supports 17 spaced apart longitudinally of the tube 12, the length of the tube 12 being, at least, as great as the width of the sheet of warp yarns 11. Each of these supports 17 comprises a ring-like portion which tightly embraces and is fixed to the tube 12. Each support also has a downwardly projecting lug 17a at its lower portion in which an anti-friction roll 17b is journaled. The rolls 17b rest upon a fixed horizontal guide G which may be part of the loom frame. There is thus provided a carriage for the whip rolls or back-rest so that the latter may be moved bodily, forwardly or rearwardly. Each support 17 also comprises an integral, elongate, normally, subst-antially horizontal arm 17x projecting rearwardly from the upper part of its ring-like portion and which is connected at its free or rear end by a pivot pin 2% to the upper end of a lever 21. The axes of the pivot pins (when the parts occupy the normal position illustrated in FIG. 1), are in the plane of the warp sheet formed by the warp yarns 11. The several levers 21 are pivotally supported upon corresponding brackets 22 (FIG. 1) mounted on the loom frame, each bracket having a pivot element 22a with its axis parallel to that of the warp beam upon which its lever 21 is mounted to turn.

The whip roll 12 rigidly unites the spaced supports 17, and the several supports, including their arms 17x, the lugs 17a, the rolls 17b and the levers 21 are here for convenience referred to as the whip roll lever assembly or merely as the lever assembly, and this assembly may rock about the points of contact of the rolls 17b with the guide G, said points of contact defining a fulcrum axis about which the lever assembly may rock.

By the above means the back-rest, comprising the tube 12, while moving forward or backward, as hereinafter described, remains parallel to the axis of the warp beam.

The several levers 21 are normally approximately vertical and connected together for simultaneous movement by having their lower ends connected by rods 23, to one or the other of hell crank levers 24 or 24a (FIG. 2), said levers all being connected to a rod 25 (or a series of connected rods) extending transversely of the loom. An extension rod 25a (FIG. 2) connects the endmost rod 25 to the upper end of a lever arm 26 (FIG. 4) fixed to a rock shaft 27. To this rock shaft there is fixed a normally, substantially horizontal arm 28 carrying a weight 2& Various parts of the loom frame are indicated by the numeral 30 in the several figures of the drawings.

Control means for the motor 13 is arranged in a casing 31 (FIGS. 3 and 5), supported on the loom frame 30' and this control means includes three switches 32, 33 and 34 (FIGS. 4 and 5) which, respectively, determine whether the motor shall turn in the forward direction, stop, or turn in the reverse direction, respectively. These switches are actuated by upwardly divergent cam fingers 32a, 33a and 34a respectively, fixed to a shaft 35 (FIG. 4). Also fixed to this shaft 35 and outside of the casing 31, there is an arm 36 (FIGS. 4 and 5) connected by a link 37 (FIG. 4) to an arm 38 fixed to the shaft 27 above described. The cam fingers 32a, 33a and 34a are arcuately spaced as substantially shown in FIG. 4.

In the wiring diagram of FIG. .6, .the numerals 30 and '40 designate relays electrical-1y connected for actuation by the switches 32 and respectively, and operating control switches 41 and 42 respectively, for a three-phase electric motor 13 and its combined electromagnetic bra'ke (not here shown), the motor receiving current from a supply indicated at 43. As shown in FIG. 6, the switches are positioned so that the motor '13 is stopped.

In operation, as the warp yarns 11 are taken up'by the loom, the sensitive back-rest comprising the tube 12 is drawn to the left in FIG. 1, causing the levers 21 to turn counterclockwise about their pivots 22a. Such movement of the back-rest due to the tensioning action of the cloth take-up (not here shown), is opposed by the rearwardly directed force of the weight 29 acting through the arm 26, the connecting rods 25 and 25a and the bell cranks 24 and 24a. By means of'the lever arm 38 (FIG. 3), the link 37 and the rocker arm 36, the shaft 35 (FIGS. 4 and 5) is turned clockwise thus moving the finger 33a so as to close the circuit at switch 33 and bringing the finger 32a into engagement with the switch 32 to close the circuit for the relays 39 and 40 (FIG. 6). The motor 13 is thus started in the forward direction (while its electromagnetic brake is released), so as to drive the warp beam clockwise, as viewed in FIG. 1, thus letting oif warps and continues to turn, even though the arm 32a has moved so as to open the switch 32, until the arm 33a engages and breaks the circuit at switch 33, thus releasing the relay and causing the motor to stop and its brake to be aplied until further warp is required when this action is repeated.

Should the take-up be turned back, either manually or by power drive, thereby slackening the warp yarns, the sensitive back-rest will thereby be allowed to move to the night, as shown in FIG. 1, in response to the weight 29 which will then descend and turn the shaft 85 in the counterclockwise direction thus bringing the finger 34a into engagement with the switch 34 to close the circuit of the relays 40 and 42. This starts the motor to turn the beam in the reverse direction thereby to wind on or rewind the warp yarn. As the warp tension is restored, the weight 29 rises, the shaft 35 turns in a clockwise direction, and the motor stops when the motor 33a engages and actuates to stop switch 33. If the take-up is now further turned back, the switch 34 will again be operated as just described to cause the beam to wind on or rewind the warp yarns and the operation may be repeated as many times as is necessary to provide for as much back winding as may be required. The let-01f motion is therefore always ready to operate in normal manner when weaving is recommenced and operates automatically, as described.

In the modification shown in FIGS. 7, 8 and 9, a further arm '43 is shown as attached to the shaft 27 and connected to a piston rod 44 attached to a piston 45 located in a hydraulic cylinder 46. The base of this cylinder is flexibly anchored to the loom framing. Fluid is maintained in the upper and lower ends of the cylinder from a reservoir 47 through valves 48 and 49' respectively, but such valves are urged by springs 48a and 45a respectively toward the closed position. A cam 50 on the crankshafts of the loom is so arranged, as to position a tappet 51 to hold both valves open, except during a period commencing just before beat-up of the lay and for a short period thereafter. However, when the valves are closed the piston 45 is hydraulically locked from movement and so prevents rotation of the shaft 27. Thus during the periods above referred to the back-rest is rigidly held from movement. Because of such locking of the shaft 27 against rotation, the shock of beat-up on the warps cannot cause the weight 29 to be bounced up and down and any resultant tension shocks from such bouncing are avoided. Equally important, at least, however, is the fact that locking the shaft 27 against rotation also prevents movement of the shaft 35 so that the electric switches coupled thereto through the link 37 and arm 36 are held stationary for the same short period.

As shown alsoin FIG. 7, a further cam .52 on a shaft S driven in time With the crankshaft is arranged to actuate an isolating switch 53. As shown in the wiring diagram, FIG. 9, the contactor switches 41 and 42 for the motor are actuated by additional solenoids 41a and 42a, compared withthe arrangement'of FIG. 6, and the switch "5 3 is arranged to cut out these solenoids during the locked period aforesaid, so that the motor cannot be actuated at that time.

As shown in the timing diagram (FIG. 8), the cam 50 is shaped to give a locked period symmetrically disposed on each side of the front dead centre of the crankshaft and represented by the angle a. This leaves an angle of approx mately 270 of rotation of-the crankshaft for the working of the motor which drives the warp beam. The cam 52 is sodesigned as to prevent operation of the beam-driving motor through a longer period, as indicated by the angle B.

In the case of very wide looms, the available warp beam winding equipment may not be capable of winding a beam of the full length to suit the loom. In such cases, each half-beam may be wound separately, in consequence of which they must be separately controlled as regards their rate of let-off in the loom.

To meet with this requirement, positive let-off mechanism as herein described is provided at both ends of the wide loom, each mechanism actuating one half-beam. In a corresponding manner, the sensitive back-rest is constructed in two separate and separately weighted halves, each half back-rest being adapted to control its adjacent half-beam let-off mechanism in the manner herein particularly described.

We claim:

1. A let-off motion for use in a conventional weaving loom of the kind which includes a power-driven warp beam, a cloth take-up, warp shedding means, a lay for beating up the weft, and a power-driven crankshaft which makes one revolution for each cycle of operation of the loom, said let-off motion comprising a whip roll and a support therefor, said support being movable toward and from the front of the loom and being so located that the whip roll contacts warp yarns which extend between the warp beam and the cloth take-11p, and means yieldably unging said whip roll support in a direction such as to tension said warp yarns, in combination, means operative positively to lock the whip roll support so as to prevent motion thereof dtu'ing that period in the cycle of the loom wherein the lay is beating up the weft, and wherein, for driving the warp beam, there is a reversible threephase electric motor; motor control means responsive to the motion of the whip ro'll, said control means comprisirrg three switches; three divergent fingers fixed to a rock shaft which is so connected to the whip roll as to rock in one direction or the other in response to motion of the whip roll, one of the switches, when closed, being operative to start the motor to turn in one direction, a second of said switches, when closed, being operative to start the motor in the opposite direction, and the third of said switches being normally open, but being closed by its respective controlling finger simultaneously with the closing of either of the other switches, and a holding relay in series with each, respectively, of the first-named two switches and which is operative to keep the motor circuit closed and the motor running until the relay circuit is broken at the third of said switches.

2. A let-01f motion according to claim 1, further characterized in having a fourth switch, actuatable by a cam turning in time with the crankshaft of the loom, which is arranged to break the circuit of the motor which drives the warp beam during that period in which the lay is beating up the weft.

3. In a loom having a power-driven crankshaft, a movable back-rest for tensioning the warp, electrically-actuated means operative to rotate the warp beam in either of opposite directions respectively, means normally operative to supply electrical current to said electrically-actuated means, control mean-s for said electrically-actuated means responsive to the position of the movable backrest, means for locking the back-rest against movement during the beat-up of the loom, and means for controlling the supply of current to said electrically-actuated means comprising three limit switches in the circuit of said electrically-actuated means, two holding relays each controlled by one, respectively, of said switches and which are operative, when energized, to keep the warp beam turning in one direction or the other respectively, a rock shaft connected to the back-rest so as to be rocked in one direction or the other as the back-rest moves forwardly or rearwardly, three cam elements axially and radially spaced from each other and fixed to said rock shaft, each of said cam elements being operative, at times, to close one of said limit switches respectively, two of said limit switches each being operative, respectively, when closed, to close the circuit of a corresponding one of said holding relays, and the third limit switch being operative, when closed, to complete the energizing circuit of one or the other of said holding relays respectively and, when open, to break the enengizing circuit of both of said holding relays.

References Cited in the file of this patent UNITED STATES PATENTS 2,375,3'16 Moessinger May 8, 1945 2,430,639 Jacques Nov. 11, 1947 2,775,415 Rush et al. Dec. 25, 1956 FOREIGN PATENTS 1,199,830 France June 22, 1959 

1. A LET-OFF MOTION FOR USE IN A CONVENTIONAL WEAVING LOOM OF THE KIND WHICH INCLUDES A POWER-DRIVEN WARP BEAM, A CLOTH TAKE-UP, WARP SHEDDING MEANS, A LAY FOR BEATING UP THE WEFT, AND A POWER-DRIVEN CRANKSHAFT WHICH MAKES ONE REVOLUTION FOR EACH CYCLE OF OPERATION OF THE LOOM, SAID LET-OFF MOTION COMPRISING A WHIP ROLL AND A SUPPORT THEREFOR, SAID SUPPORT BEING MOVABLE TOWARD AND FROM THE FRONT OF THE LOOM AND BEING SO LOCATED THAT THE WHIP ROLL CONTACTS WARP YARNS WHICH EXTEND BETWEEN THE WARP BEAM AND THE CLOTH TAKE-UP, AND MEANS YIELDABLY URGING SAID WHIP ROLL SUPPORT IN A DIRECTION SUCH AS TO TENSION SAID WARP YARNS, IN COMBINATION, MEANS OPERATIVE POSITIVELY TO LOCK THE WHIP ROLL SUPPORT SO AS TO PREVENT MOTION THEREOF DURING THAT PERIOD IN THE CYCLE OF THE LOOM WHEREIN THE LAY IS BEATING UP THE WEFT, AND WHEREIN, FOR DRIVING THE WARP BEAM, THERE IS A REVERSIBLE THREEPHASE ELECTRIC MOTOR; MOTOR CONTROL MEANS RESPONSIVE TO THE MOTION OF THE WHIP ROLL, SAID CONTROL MEANS COMPRISING THREE SWITCHES; THREE DIVERGENT FINGERS FIXED TO A ROCK SHAFT WHICH IS SO CONNECTED TO THE WHIP ROLL AS TO ROCK IN ONE DIRECTION OR THE OTHER IN RESPONSE TO MOTION OF THE WHIP ROLL, ONE OF THE SWITCHES, WHEN CLOSED, BEING OPERATIVE TO START THE MOTOR TO TURN IN ONE DIRECTION, A SECOND OF SAID SWITCHES, WHEN CLOSED, BEING OPERATIVE TO START THE MOTOR IN THE OPPOSITE DIRECTION, AND THE THIRD OF SAID SWITCHES BEING NORMALLY OPEN, BUT BEING CLOSED BY ITS RESPECTIVE CONTROLLING FINGER SIMULTANEOUSLY WITH THE CLOSING OF EITHER OF THE OTHER SWITCHES, AND A HOLDING RELAY IN SERIES WITH EACH, RESPECTIVELY, OF THE FIRST-NAMED TWO SWITCHES AND WHICH IS OPERATIVE TO KEEP THE MOTOR CIRCUIT CLOSED AND THE MOTOR RUNNING UNTIL THE RELAY CIRCUIT IS BROKEN AT THE THIRD OF SAID SWITCHES. 